Spring winding devices for forming coil springs have been described previously. U.S. Pat. No. 4,893,491 to Ohdai et al., issued Jan. 16, 1990 and assigned to Asahi-Seiki Manufacturing Co., Ltd., describes a spring winding machine and a method for forming coil springs. A wire is fed from a quill against a forming surface. The forming surface is moved to a forward position close to a tip of the quill by a drive system including a cam assembly under numerical control. As the wire is fed from the quill against the forming surface, the wire is bent. By rotating the forming surface, the wire fed from the quill can be bent in different directions such that coil springs of different predetermined forms and sizes are formed. After the coil spring reaches its predetermined form and size, the forming surface is withdrawn from the tip of the quill by the drive system and cam assembly and a cutting tool is moved to a forward position to cut the formed coiled spring away from the wire fed from the quill.
The spring winding device described by Ohdai et al. in the '491 patent provides various cutting and bending tools mounted on a tool mounting frame. These tools can be repositioned relative to the tip of the quill in the same manner as the forming surface. The tool mounting frame includes an opening through which the quill can pass. This allows tools to be mounted and brought in towards the quill and withdrawn from the quill from both front and rear sides of the tool mounting frame. By providing a mechanism for mounting various tools in close proximity to the tip of the quill, a wide variety of bends can be made when forming coil springs. Furthermore, by utilizing numerical control of the apparatus, coil springs can be formed which have a variety of dimensions.
In many applications, for connection of the spring in its particular application, torsion and extension springs require axial toes, e.g., toes generally axial to an axis through the spring. For example, axial toes are used to interface the spring into an electrical clutch used in copy machines which push paper repetitiously and continually. For such an application, the springs are manufactured to strict tolerances dimensionally throughout each and every wrap of the spring. These strict tolerances are extremely important with regard to the toes and the portion of a wrap of the spring connecting the toe to the rest of the spring body. The manufacture of such toes is difficult because of their axial nature. Some springs, for particular applications, require toes having a minimal length, for example, one tenth (0.1) of an inch. This minimal length leads further to the difficulty of manufacture.
Previously, generally axial toes which are formed prior to forming the spring body of a spring have been manufactured utilizing bending tools mounted on a tool mounting frame, such as the frame in Ohdai et al. described above. One bending tool is positioned next to the wire as it is fed from the quill, another bending tool bends the wire across the first bending tool, and yet another tool comes from below to overbend the wire to achieve a 90.degree. bend.
In addition, a toe formed adjacent the spring body after the spring body is formed, previously involved the use of unnecessary additional steps for such manufacture. For example, after one generally axial toe and the spring body were formed, the spring lacking a second generally axial toe was cut and removed from the quill, so that a second generally axial toe could be formed by a machine at a different location. The forming of the second toe at a different machine after the spring body is formed increases the time of manufacture because the spring must be cut from the quill and positioned at the different machine. Because of the difficulty of manufacturing springs having axial toes with precise dimensions utilizing a spring winding device such as that described in Ohdai et al., U.S. Pat. No. 4,893,491, there is a need in the art to produce springs with precise dimensions having generally axial toes and to do so in a shorter period of time than is now possible.